Zero-point adjustment of dedicated servo motor encoders is a technology possessed only by the manufacturers themselves, and is rarely known to outsiders. This involves core technology; even if some people could adjust it, the results would certainly be inaccurate. Furthermore, specialized equipment is required for adjustment. Manual adjustment alone cannot properly assemble an absolute encoder.
Now, let's learn about servo encoders through the following content.
Phase alignment method of incremental encoder
In this discussion, the output signal of the incremental encoder is a square wave signal, which can be further divided into incremental encoders with commutation signals and ordinary incremental encoders. Ordinary incremental encoders have two-phase orthogonal square wave pulse output signals A and B, and a zero-position signal Z; incremental encoders with commutation signals, in addition to the ABZ output signals, also have electronic commutation signals UVW with a 120-degree phase difference. The number of cycles per revolution of UVW is consistent with the number of pole pairs of the motor rotor. The alignment method between the phase of the UVW electronic commutation signal of the incremental encoder with commutation signals and the rotor pole phase, or electrical angle phase, is as follows:
1. Apply a DC current less than the rated current to the UV windings of the motor using a DC power supply, with U as the input and V as the output, to orient the motor shaft to a balanced position;
2. Observe the U-phase and Z-phase signals of the encoder using an oscilloscope;
3. Adjust the relative position of the encoder shaft and the motor shaft;
4. While adjusting, observe the encoder's U-phase signal transition edge and Z signal until the Z signal stabilizes at a high level (assuming the Z signal is normally low). Then lock the relative position of the encoder and the motor.
5. Twist the motor shaft back and forth. If the Z signal remains stable at a high level each time the motor shaft freely returns to its balanced position, then the alignment is effective.
After disconnecting the DC power supply, the following verification was performed:
1. Use an oscilloscope to observe the U-phase signal of the encoder and the back EMF waveform of the UV lines of the motor;
2. When the motor shaft is rotated, the rising edge of the encoder's U-phase signal coincides with the zero-crossing point of the motor's UV-line back EMF waveform from low to high. The encoder's Z signal also appears at this zero-crossing point.
The verification method described above can also be used as an alignment method.
It is important to note that at this point, the phase zero point of the incremental encoder's U-phase signal is aligned with the phase zero point of the motor's UV line back EMF. Since the motor's U-phase back EMF differs from the UV line back EMF by 30 degrees, this alignment brings the phase zero point of the incremental encoder's U-phase signal to the -30-degree phase point of the motor's U-phase back EMF. Since the phase of the motor's electrical angle is consistent with the phase of the U-phase back EMF waveform, the phase zero point of the incremental encoder's U-phase signal is aligned with the -30-degree point of the motor's electrical angle phase.
Some servo manufacturers are accustomed to directly aligning the zero point of the encoder's U-phase signal with the zero point of the motor's electrical angle. To achieve this, one can:
1. Connect three resistors of equal resistance in a star configuration, and then connect the three star-connected resistors to the UVW three-phase winding leads of the motor respectively;
2. By observing the midpoint between the motor's U-phase input and the star resistor using an oscilloscope, the U-phase back EMF waveform of the motor can be approximately obtained;
3. Adjust the relative position of the encoder shaft and the motor shaft, or the relative position of the encoder housing and the motor housing, according to ease of operation;
4. While adjusting, observe the rising edge of the encoder's U-phase signal and the zero-crossing point of the motor's U-phase back EMF waveform from low to high. Finally, make the rising edge and the zero-crossing point coincide, lock the relative position relationship between the encoder and the motor, and complete the alignment.
Since ordinary incremental encoders do not have UVW phase information, and the Z signal can only reflect a point within one revolution, they do not have direct phase alignment potential, and therefore are not the topic of this discussion.
Phase alignment method of absolute encoder
For absolute encoders, phase alignment makes little difference between single-turn and multi-turn encoders; essentially, it involves aligning the encoder's detection phase with the motor's electrical angle phase within one revolution. Early absolute encoders used a separate pin to provide the highest bit level of the single-turn phase. By toggling the 0 and 1 values of this level, encoder-motor phase alignment could also be achieved, as follows:
1. Apply a DC current less than the rated current to the UV windings of the motor using a DC power supply, with U as the input and V as the output, to orient the motor shaft to a balanced position;
2. Observe the highest count bit level signal of the absolute encoder using an oscilloscope;
3. Adjust the relative position of the encoder shaft and the motor shaft;
4. While adjusting, observe the transition edge of the highest count signal until the transition edge accurately appears at the directional balance position of the motor shaft, then lock the relative position of the encoder and the motor;
5. Twist the motor shaft back and forth. If the jump edge can be accurately reproduced each time the motor shaft freely returns to the balance position, then the alignment is effective.
These types of absolute encoders have been widely replaced by newer absolute encoders using serial protocols such as EnDAT, BiSS, and Hyperface, as well as Japanese-specific serial protocols. Consequently, the highest bit signal no longer exists, and the method for aligning the encoder and motor phases has changed. One very practical method is to utilize the encoder's internal EEPROM to store the measured phase after the encoder is randomly installed on the motor shaft. The specific method is as follows:
1. Install the encoder randomly on the motor, that is, fix the encoder shaft to the motor shaft, and the encoder housing to the motor housing;
2. Apply a DC current less than the rated current to the UV windings of the motor using a DC power supply, with U as the input and V as the output, to orient the motor shaft to a balanced position;
3. Use a servo driver to read the single-turn position value of the absolute encoder and store it in the EEPROM inside the encoder that records the initial phase of the motor's electrical angle;
4. The alignment process is complete.
Since the motor shaft is now oriented at -30 degrees of the electrical angle phase, the position detection value stored in the encoder's internal EEPROM corresponds to the -30 degree phase of the motor's electrical angle. Subsequently, the driver subtracts this stored value from the single-turn position detection data at any given time, performs necessary conversions based on the number of motor pole pairs, and adds -30 degrees to obtain the motor's electrical angle phase at that moment.
This alignment method requires the support and cooperation of both the encoder and the servo drive. The fundamental reason why the encoder phase of Japanese servo motors is not easily adjustable by end users is that they refuse to provide users with a functional interface and operation method for this alignment method. A major advantage of this alignment method is that it only requires providing a rotor directional current with a defined phase sequence and direction to the motor windings, without needing to adjust the angular relationship between the encoder and the motor shaft. Therefore, the encoder can be directly mounted on the motor at any initial angle without the need for fine, or even simple, adjustments. It is easy to operate and has good manufacturability.
If the absolute encoder lacks both a usable EEPROM and a pin for detecting the highest count bit, the alignment method becomes relatively complex. If the driver supports reading and displaying single-turn absolute position information, then the following can be considered:
1. Apply a DC current less than the rated current to the UV windings of the motor using a DC power supply, with U as the input and V as the output, to orient the motor shaft to a balanced position;
2. Use a servo driver to read and display the single-turn position value of the absolute encoder;
3. Adjust the relative position of the encoder shaft and the motor shaft;
4. After the above adjustments, the displayed single-turn absolute position value is made sufficiently close to the single-turn absolute position point corresponding to -30 degrees of electrical angle of the motor calculated based on the number of pole pairs of the motor, and the relative position relationship between the encoder and the motor is locked;
5. Twist the motor shaft back and forth. If the calculated position points can be accurately reproduced each time the motor shaft freely returns to the balance position, then the alignment is effective.
If users cannot even obtain the absolute value information, they can only rely on the manufacturer's specialized tooling to simultaneously detect the absolute position and the motor's electrical angle phase. Using this tooling, the relative angular position relationship between the encoder and the motor is adjusted to align the encoder phase with the motor's electrical angle phase before locking. This makes it even more impossible for users to resolve the encoder phase alignment issue themselves.
I personally recommend storing the initial installation position in the EEPROM. This method is simple, practical, adaptable, and easy to make available to users so that they can install the encoder themselves and complete the phase setting of the motor's electrical angle.
Phase alignment method of sine and cosine encoders
A typical sine and cosine encoder has a pair of orthogonal sin, cos1Vp-p signals, which are equivalent to the AB quadrature signals of an incremental encoder with square wave signals. These signals repeat many times per revolution, such as 2048. It also has a narrow-amplitude symmetrical triangular wave Index signal, which is equivalent to the Z signal of an incremental encoder. It usually appears once per revolution. This type of sine and cosine encoder is essentially an incremental encoder. Another type of sine and cosine encoder, in addition to the aforementioned orthogonal sin and cosine signals, also possesses mutually orthogonal 1Vp-p sinusoidal C and D signals that appear in only one signal cycle per revolution. If the C signal is sin, then the D signal is cos. Through high-ratio subdivision technology of sin and cosine signals, the sine and cosine encoder can obtain a more refined nominal detection resolution than the original signal cycle. For example, a 2048-line sine and cosine encoder, after being subdivided by 2048, can achieve a nominal detection resolution of more than 4 million lines per revolution. Currently, many European and American servo manufacturers provide this type of high-resolution servo system, while it is still rare among domestic manufacturers. Furthermore, the C and D signals of the sine and cosine encoder with C and D signals, after being subdivided, can also provide higher absolute position information per revolution, such as 2048 absolute positions per revolution. Therefore, the sine and cosine encoder with C and D signals can be regarded as a kind of analog single-turn absolute encoder.
The initial electrical angle phase alignment method for a servo motor using this encoder is as follows:
1. Apply a DC current less than the rated current to the UV windings of the motor using a DC power supply, with U as the input and V as the output, to orient the motor shaft to a balanced position;
2. Observe the C signal waveform of the sine and cosine encoder using an oscilloscope;
3. Adjust the relative position of the encoder shaft and the motor shaft;
4. While adjusting, observe the C signal waveform until the zero-crossing point, from low to high, accurately appears at the directional balance position of the motor shaft, then lock the relative position of the encoder and the motor;
5. Twist the motor shaft back and forth. If the zero-crossing point is accurately reproduced each time the motor shaft freely returns to the balance position, the alignment is effective.
After disconnecting the DC power supply, the following verification was performed:
1. Use an oscilloscope to observe the C-phase signal of the encoder and the back EMF waveform of the UV line of the motor;
2. Rotate the motor shaft. The zero-crossing point of the encoder's C-phase signal from low to high coincides with the zero-crossing point of the motor's UV line back EMF waveform from low to high.
This verification method can also be used as an alignment method.
At this point, the zero-crossing point of the C signal is aligned with the -30 degree point of the electrical angle phase of the motor.
If you want to align directly with the 0-degree point of the motor's electrical angle, you can consider:
1. Connect three resistors of equal resistance in a star configuration, and then connect the three star-connected resistors to the UVW three-phase winding leads of the motor respectively;
2. By observing the midpoint between the motor's U-phase input and the star resistor using an oscilloscope, the U-phase back EMF waveform of the motor can be approximately obtained;
3. Adjust the relative position of the encoder shaft and the motor shaft;
4. While adjusting, observe the zero-crossing points of the encoder's C-phase signal from low to high and the zero-crossing points of the motor's U-phase back EMF waveform from low to high. Finally, make the two zero-crossing points coincide, lock the relative position relationship between the encoder and the motor, and complete the alignment.
Since ordinary sine and cosine encoders do not have phase information within one revolution, and the index signal can only reflect one point within one revolution and does not have direct phase alignment potential, they will not be discussed here.
If a servo drive that can be connected to a sine and cosine encoder can provide the user with single-turn absolute position information obtained from C and D, then it can be considered:
1. Apply a DC current less than the rated current to the UV windings of the motor using a DC power supply, with U as the input and V as the output, to orient the motor shaft to a balanced position;
2. Use a servo driver to read and display the single-turn absolute position information obtained from the C and D signals;
3. Adjust the relative position of the resolver shaft and the motor shaft;
4. After the above adjustments, ensure that the displayed absolute position value is sufficiently close to the absolute position point corresponding to -30 degrees electrical angle of the motor calculated based on the number of pole pairs, and lock the relative position relationship between the encoder and the motor;
5. Twist the motor shaft back and forth. If the calculated absolute position point can be accurately reproduced each time the motor shaft freely returns to the balance position, then the alignment is effective.
Afterwards, after removing the DC power supply, the alignment verification effect is basically the same as before:
1. Use an oscilloscope to observe the C-phase signal of the sine/cosine encoder and the back EMF waveform of the motor's UV lines;
2. Rotate the motor shaft to verify that the zero-crossing point of the encoder's C-phase signal from low to high coincides with the zero-crossing point of the motor's UV line back EMF waveform from low to high.
If the non-volatile memory such as EEPROM inside the driver is used, the phase measured after the sine and cosine encoders are randomly installed on the motor shaft can also be stored. The specific method is as follows:
1. Randomly install the sine and cosine encoders on the motor, i.e., fix the encoder shaft to the motor shaft, and the encoder housing to the motor housing;
2. Apply a DC current less than the rated current to the UV windings of the motor using a DC power supply, with U as the input and V as the output, to orient the motor shaft to a balanced position;
3. Use a servo driver to read the single-turn absolute position value parsed from the C and D signals, and store it in a non-volatile memory such as an EEPROM inside the driver that records the initial installation phase of the motor's electrical angle;
4. The alignment process is complete.
Since the motor shaft is now oriented at -30 degrees of the electrical angle phase, the position detection value stored in the driver's internal non-volatile memory (such as EEPROM) corresponds to the -30-degree phase of the motor's electrical angle. Subsequently, the driver subtracts this stored value from the absolute position value related to the electrical angle obtained from the encoder at any given time, performs necessary conversions based on the number of motor pole pairs, and adds -30 degrees to obtain the motor's electrical angle phase at that moment.
This alignment method requires support and cooperation from the servo driver in terms of both domestic and operational aspects. Moreover, since the non-volatile memory such as EEPROM that records the initial phase of the motor's electrical angle is located in the servo driver, once aligned, the motor and driver are effectively bound together. If the motor, sine/cosine encoder, or driver needs to be replaced, the initial installation phase alignment operation needs to be performed again, and the matching relationship between the motor and driver needs to be re-bound.
Phase alignment method of rotary transformer
A resolver, or simply resolver, is composed of high-performance silicon steel laminations and enameled wire with special electromagnetic design. Compared to encoders using photoelectric technology, it has the ability to adapt to harsh working environments such as heat resistance, vibration resistance, shock resistance, oil resistance, and even corrosion resistance. Therefore, it is widely used in harsh applications such as weapon systems. A single-pole (single-speed) resolver can be regarded as a single-turn absolute feedback system and is the most widely used. Therefore, this discussion will focus on single-speed resolvers. When multi-speed resolvers are paired with servo motors, I personally believe that the number of pole pairs should ideally be a factor of the number of pole pairs of the motor, to facilitate the correspondence between motor speed and pole pair decomposition.
A resolver typically has six signal leads, divided into three groups, corresponding to one excitation coil and two orthogonal induction coils. The excitation coil receives the input sinusoidal excitation signal, while the induction coils, based on the relative angular positions of the resolver's rotor and stator, induce detection signals with SIN and COS envelopes. The resolver's SIN and COS output signals are the modulation results of the excitation sinusoidal signal based on the angle between the rotor and stator. If the excitation signal is sinωt and the angle between the rotor and stator is θ, then the SIN signal is sinωt × sinθ, and the COS signal is sinωt × cosθ. Based on the SIN, COS signals and the original excitation signal, a high-resolution position detection result can be obtained through necessary detection circuitry. Currently, the detection resolution of commercial resolver systems can reach 2^12 per revolution, or 4096, while scientific research and aerospace systems can even reach 2^20 or higher, although the size and cost are also considerable.
The method for aligning the electrical angle phase of a commercial resolver and a servo motor is as follows:
1. Apply a DC current less than the rated current to the UV windings of the motor using a DC power supply, with U as the input and V as the output;
2. Then, observe the signal lead output of the resolver's SIN coil using an oscilloscope;
3. Adjust the relative position of the resolver rotor on the motor shaft to the motor shaft, or the relative position of the resolver stator to the motor housing, according to ease of operation;
4. While adjusting, observe the envelope of the resolver SIN signal, and continue adjusting until the amplitude of the signal envelope is completely zero, then lock the resolver;
5. Twist the motor shaft back and forth. If the zero-crossing point of the signal envelope amplitude can be accurately reproduced each time the motor shaft freely returns to the equilibrium position, then the alignment is effective.
Disconnect the DC power supply and perform alignment verification:
1. Observe the SIN signal of the resolver and the back EMF waveform of the UV line of the motor using an oscilloscope;
2. Rotate the motor shaft to verify that the zero-crossing point of the resolver's SIN signal envelope coincides with the zero-crossing point of the motor's UV line back EMF waveform from low to high.
This verification method can also be used as an alignment method.
At this point, the zero-crossing point of the SIN signal envelope is aligned with the -30 degree point of the motor's electrical angle phase.
If you want to align directly with the 0-degree point of the motor's electrical angle, you can consider:
1. Connect three resistors of equal resistance in a star configuration, and then connect the three star-connected resistors to the UVW three-phase winding leads of the motor respectively;
2. By observing the midpoint between the motor's U-phase input and the star resistor using an oscilloscope, the U-phase back EMF waveform of the motor can be approximately obtained;
3. Adjust the relative position of the encoder shaft and the motor shaft, or the relative position of the encoder housing and the motor housing, according to ease of operation;
4. While adjusting, observe the zero-crossing point of the SIN signal envelope of the resolver and the zero-crossing point of the motor U-opposite electromotive force waveform from low to high. Finally, make these two zero-crossing points coincide, lock the relative position relationship between the encoder and the motor, and complete the alignment.
It should be noted that in the above operation, it is necessary to effectively distinguish between the positive and negative half-cycles of the resolver's SIN envelope signal. Since the SIN signal is the result of modulating the excitation signal with the sinθ value (the angle between the rotor and stator), the modulated excitation signal in the SIN signal envelope corresponding to the positive half-cycle of sinθ is in phase with the original excitation signal, while the modulated excitation signal in the SIN signal envelope corresponding to the negative half-cycle of sinθ is out of phase with the original excitation signal. Based on this, the positive and negative half-cycles in the waveform of the resolver's output SIN envelope signal can be distinguished. When aligning, it is necessary to take the zero-crossing point of the SIN envelope signal corresponding to the transition point from the negative half-cycle to the positive half-cycle of sinθ. If it is reversed, or if an accurate judgment is not made, the electrical angle after alignment may be misaligned by 180 degrees, which may cause the speed outer loop to enter positive feedback.
If a servo driver that can be connected to a resolver can provide the user with absolute position information related to the motor's electrical angle obtained from the resolver signal, then it is worth considering:
1. Apply a DC current less than the rated current to the UV windings of the motor using a DC power supply, with U as the input and V as the output, to orient the motor shaft to a balanced position;
2. Use a servo driver to read and display the absolute position information related to the motor's electrical angle obtained from the resolver signal;
3. Adjust the relative position of the resolver shaft and the motor shaft, or the relative position of the resolver housing and the motor housing, according to ease of operation;
4. After the above adjustments, ensure that the displayed absolute position value is sufficiently close to the absolute position point corresponding to -30 degrees electrical angle of the motor calculated based on the number of pole pairs, and lock the relative position relationship between the encoder and the motor;
5. Twist the motor shaft back and forth. If the calculated absolute position point can be accurately reproduced each time the motor shaft freely returns to the balance position, then the alignment is effective.
Afterwards, after removing the DC power supply, the alignment verification effect is basically the same as before:
1. Observe the SIN signal of the resolver and the back EMF waveform of the UV line of the motor using an oscilloscope;
2. Rotate the motor shaft to verify that the zero-crossing point of the resolver's SIN signal envelope coincides with the zero-crossing point of the motor's UV line back EMF waveform from low to high.
If the driver's internal non-volatile memory, such as EEPROM, is used, the measured phase after the resolver is randomly installed on the motor shaft can also be stored. The specific method is as follows:
1. The resolver is randomly installed on the motor, that is, the resolver shaft is fixed to the motor shaft, and the resolver housing is fixed to the motor housing;
2. Apply a DC current less than the rated current to the UV windings of the motor using a DC power supply, with U as the input and V as the output, to orient the motor shaft to a balanced position;
3. Use a servo driver to read the absolute position value related to the electrical angle obtained from the resolver, and store it in a non-volatile memory such as an EEPROM that records the initial installation phase of the motor's electrical angle;
4. The alignment process is complete.
Since the motor shaft is now oriented at -30 degrees of the electrical angle phase, the position detection value stored in the driver's internal non-volatile memory (such as EEPROM) corresponds to the -30-degree phase of the motor's electrical angle. Subsequently, the driver subtracts this stored value from the absolute position value related to the electrical angle obtained from the resolver at any given time, performs necessary conversions based on the number of motor pole pairs, and adds -30 degrees to obtain the motor's electrical angle phase at that moment.
This alignment method requires support and cooperation from the servo driver in terms of both domestic and operational aspects. Moreover, since the non-volatile memory such as EEPROM that records the initial phase of the motor's electrical angle is located in the servo driver, once aligned, the motor and driver are effectively bound together. If the motor, resolver, or driver needs to be replaced, the initial installation phase alignment operation must be performed again, and the matching relationship between the motor and driver must be re-bound.
Notice
1. In the above discussion, the so-called alignment to the -30-degree phase of the motor electrical angle is based on the premise that the UV back EMF waveform lags behind the U phase by 30 degrees.
2. In the above discussion, the UV phase is energized and the back EMF waveform of the UV line is referenced as an example. Some servo systems may use the UW phase to be energized and the back EMF waveform of the UW line as a reference for alignment.
3. If you want to directly align to the 0-degree phase point of the motor's electrical angle, you can connect the U phase to the positive terminal of a low-voltage DC power source, and connect the V and W phases in parallel to the negative terminal of the DC power source. In this case, the orientation angle of the motor shaft will be offset by 30 degrees relative to the series energization of the UV phases. After aligning using the corresponding alignment method given in the text, it will, in principle, be aligned to the 0-degree phase of the motor's electrical angle, without the -30-degree offset. This seems advantageous, but considering the inconsistency of the motor winding parameters, the currents flowing through the V and W phase windings after the V and W phases are connected in parallel are likely to be inconsistent, thus affecting the accuracy of the motor shaft orientation angle. However, when the UV phases are energized, the U and V phase windings are simply in series, so the currents flowing through the U and V phase windings are necessarily consistent, and the accuracy of the motor shaft orientation angle will not be affected by the winding orientation current.
4. It's possible that servo manufacturers intentionally misalign the initial phase, especially in feedback systems that provide absolute position data. In such cases, the initial phase misalignment can be easily compensated for by the data offset, perhaps serving as a way to protect their product line. However, this leaves users with even less information about the correct initial phase alignment of the servo motor feedback components. Naturally, users would prefer not to encounter such a supplier.
To add to the above statement:
In modern systems, such as Fagor system version 6.02 and above, the parameters of the Fagor synchronous motor can be automatically adjusted after the encoder is installed. This eliminates the need for such time-consuming adjustments.
Example of servo motor encoder zeroing and alignment method
An AB servo motor (MPL-B640F-MJ24AA) was disassembled for brake inspection. Due to the customer's inexperience, the encoder fixed to the tail of the motor was also removed (without being marked). The encoder is a Sick SRM50-HFA0-K01. After reinstalling it, the brakes worked fine, but a runaway malfunction occurred. The servo driver reported errors E18 OVERSPEED or E24 velocityerror.
The emergency zeroing method is simple and practical. However, the motor must be removed from the equipment and adjusted using the equipment. After testing, it can be reinstalled. In fact, after a lot of zeroing tests, each servo motor has a zero-speed stationary region of less than 10 degrees and a high-speed reverse region of 350 degrees. If you only occasionally replace an encoder, this is indeed too troublesome. Here is a very simple emergency method that can solve the problem quickly.
Remove the damaged encoder, install a new encoder, and fix it to the shaft. Allow the adjustable base to suspend and rotate freely. Reconnect the motor to the circuit, set the machine speed to zero, and after powering on normally, press the start switch. Several scenarios may occur.
1. The motor is reversing at high speed. This is because the encoder is too far from the actual zero position. Don't panic. You can rotate the encoder by an angle until the motor can come to a stop.
2. When the motor is stationary under the zero-speed command, carefully rotate the encoder counterclockwise. Note: be very slow. Continue rotating until the motor starts to reverse at high speed. Note this position and immediately return to the stationary area. This requires simultaneous operation with both hands: one hand rotating the encoder while the other holds a marker. Remember to be quick and avoid panicking; this is normal. Then continue rotating slowly clockwise until another high-speed reverse occurs. Note this position and immediately return to the stationary area.
Through the above adjustments, you will find that the incremental servo motor actually has a relatively wide adjustable range, and the middle position of this range is the maximum torque output point of the servo motor. If a motor has insufficient torque or insufficient torque in one direction when running in both directions, it is often because the encoder's Z signal is weakened or the position is off-center, that is, the zero position has deviated. Generally, readjusting the zero position will solve the problem.
For a new encoder, this stationary region is relatively small. If it increases significantly, it indicates a problem with the encoder's internal circuitry, manifesting as insufficient torque or a significant increase in heat generation. When measured with an ammeter, the no-load current will show a marked increase.
After locating the center position and cleaning it, simply fix the encoder base directly to the corresponding spot on the side of the motor using 502 glue. Once the 502 glue is dry, apply a layer of silicone rubber before putting it into normal operation. Practice has shown that under normal circumstances, a servo motor treated in this way can last for a year without any problems.
As can be seen from the above adjustments, since the encoder shaft and the motor shaft can be connected at any angle, the encoder zero position and the mechanical position of the motor are only relative. Only when the encoder shaft and the motor shaft are fixed, the actual zero position of the encoder is also fixed. If the position of the movable base is determined, then the position of the post head screw between the shafts is also fixed.
